Are the claimed benefits of fluoride-fluoridation over-rated

Is fluoride ingestion and topical fluorides the principal factors involved in the decline of tooth decay in the last 50 years or are there other factors involved in the decreasing caries rates?

Dentistry maintains that fluoride ingestion and topical fluorides are the principal factors involved in the decline of tooth decay in the last 50 years. Are there other factors involved in the decreasing caries rates?

Are children ingesting too much fluoride? What are the main and hidden sources of fluoride intake?

Examination of five recent studies of preventive dental care discloses widely varying estimates of its costs, effects, and benefits. Further, the studies reveal that there is much room for improvement in both methods of measurement and analytical strategies. Two of the studies report on low-cost, highly effective hypothetical programs of care; the other three report on field trials with actual costs ten times as large as hypothetical programs and sometimes nonexistent effects on tooth decay. [...] Measurement of the effects of preventive dental care requires careful matching of treatment and control groups; a better understanding of the relationships among tooth decay, preventive care, individual characteristics, and environmental factors; and a change in perspective from the static "surfaces saved" to the dynamic "rate of decay." Extrapolation of treatment-effectiveness results from small-scale clinical or field trials to hypothetical situations, as widely practiced in the literature, is simply not warranted by available evidence. [emphasis added]

Hathaway WE, et al., A Study Into the Effects of Light on children of Elementary School Age -- A Case of Daylight Robbery, 1992 Feb, Policy and Planning Branch, Planning and Information Services Division, Alberta Education, ISBN -7732-0724-4

Hattab FN, The state of fluorides in toothpastes, Journal of Dentistry, 1989 Apr, 17(2), 47-54

Formulating an effective toothpaste formula requires that fluoride (F) in toothpaste must be made available to the enamel microenvironment in reactive form (bioactive). The aims of this study were to evaluate the compatibility of F with the abrasives (cleaning and polishing agents) used in toothpaste formulations and to monitor the effect of ageing on availability of F in NaF/abrasive mixtures as well as in toothpaste formulations. There was a great variation in the rate and extent of loss of F in the NaF/abrasive mixtures and in the toothpaste formulas. Addition of NaF solution to aluminium- and calcium-containing abrasives resulted in losses of 60-90 per cent of the added F after 1 week's storage at room temperature. At 1 month of age, calcium phosphate dihydrate and aluminium silicate adsorb about four times more F than calcium carbonate. On the other hand, sodium bicarbonate and sodium metaphosphate inactivated 20-25 per cent of the added F after 9 months' storage. Silica was inert in binding and inactivating F of NaF and Na2PO3F (MFP). Calcium-containing abrasives were markedly more compatible with MFP than with NaF. After 12 months of storing the toothpastes, the soluble F (initial F- plus F of hydrolysed PO3F2-) in MFP-calcium carbonate/sodium silicate toothpaste was twice as much as MFP-calcium carbonate/aluminium silicate toothpaste.(abstract truncated) [emphasis added]

[editor's note: the extent of scientific knowledge today is that the topical fluoridated products must be combined with the right ingredients and at certain Ph levels or fluoride is not bioavailable to the tooth. The early fluoridated toothpastes introduced in the 1960s were not effective cavity-fighters. Recently, on U.K. television, a former Director of Colgate admitted that there was more hype than science to the early advertising claims of significant benefits to using fluoridated toothpastes. Later formulations however, do show fluoridated toothpaste has remineralization properties.

The decline in dental caries in children in North America, Scandinavia, Britain, Ireland and many Commonwealth nations is well documented. The multiple uses of fluoride can account for most, but not all, of this reduction. In this investigation, data are provided which suggest a relationship between antibiotic usage for medical purposes and a decline in both mutans streptococci (MS) and caries. Children attending Grades 1 and 2 in the Coldwater, Michigan school system and who reportedly never received antibiotics had significantly higher proportions of MS in the fissure plaques of first molars than subjects who received antibiotics. The level of decay in the primary dentition was inversely related to the reported usage of antibiotics. The frequent usage of antibiotics could reduce the incidence of dental caries by delaying the colonization of the teeth by the MS. This was evaluated by a prospective study in infants to determine what effect reported antibiotic usage would have on the colonization of newly erupting primary teeth. Only 2 of 10 infants cultured at 2 to 3 week intervals for periods up to 1 year after tooth eruption became colonized by the MS. One had never received antibiotics and the second had been on antibiotics for a single 5-day period. Seven of the 8 non-colonized infants had received antibiotic therapy for periods ranging from 10 to 181 days. Both the Coldwater study and the prospective study of infants suggested a relation between frequency of antibiotic usage for medical purposes and the MS levels on the teeth.

editor's note: the second sentence is not evidence-based -- caries have declined globally, regardless of community fluoridation status. Moreover, the onset of this decline preceded the wide-spread use of fluoridated toothpaste. In light of this study, it's a most puzzling statement when one considers that the decline in tooth decay may have started with the advent of antibiotics

Main RA, Lewis DW, Hawkins RJ, A Survey of General Dentists In Ontario, Part II: Knowledge and Use of Topical Fluoride and Dental Prophylaxis Practices, J. Canadian Dental Association, 63:8, 1997 September, 607-617.

A mail questionnaire was used to assess variations in the knowledge and practices of Ontario dentists with respect to topical fluoride and prophylaxis procedures. The questionnaire was answered by 1,276 general dentists. A high percentage (72 to 83 percent) of respondents identified six months as the optimal time interval at which both procedures should be repeated for all patients under 19 years of age. Relatively few dentists (<10 percent) indicated that there should be no specific time interval for re-treatment (i.e. that it should be individually selected). The respondents' preventive knowledge was found to be deficient in two areas: few dentists (16 percent) knew that it is not necessary to provide a prophylaxis prior to topical fluoride application to achieve maximum caries protection; and most dentists overestimated the speed of caries progress from outer enamel to the dentinoenamel junction (DE) in both primary (83 percent) and permanent (82 per cent) approximal tooth surfaces, in bivariate analysis, three variables were found to be consistently and significantly related to optimal time intervals selected for both topical fluoride application and prophylaxis procedures: year of graduation from dental school; level of hygienist employment; and percentage of patients with private insurance. Multivariate analysis also identified three significant variables: year of graduation from dental school; level of dental hygienist employment; and practice busyness. Continuing education courses are suggested as a means of updating dentists' knowledge regarding preventive services. Studies are needed to determine the extent to which recent recommendations regarding the professional application of topical fluorides have been followed.

The relative efficacy of NaF silica toothpastes containing 1000 ppm fluoride and 1500 ppm fluoride in the control of dental caries is not clear-cut. Also, it has not been established that incorporation of trimetaphosphate (TMP) improves the anticaries activity of NaF toothpastes. A three-year clinical trial was conducted to test the hypotheses that: (i) the anticaries activity of NaF toothpastes containing 1500 ppm F was greater than that of NaF toothpastes containing 1000 ppm F, and (ii) inclusion of TMP improved the efficacy of NaF silica pastes. Subsidiary aims included determination of whether frequency of toothbrushing and method of rinsing after brushing were correlated with caries increments. The study involved 4196 children aged 11 to 12 years at outset. These participants had been selected from a pool of 7374 potential subjects on the basis of caries experience and dental eruption pattern. They were stratified by sex, examiner, and presence of calculus and caries, and were allocated at random to one of the four toothpastes under study. Using mirror and probe and also FOTI, we carried out clinical examinations at baseline and annually thereafter for 3 yrs. Bitewing radiographs of a subset of children were taken at baseline and at the end of the study. The outcome measure for the study, DMFS increment, was defined as the increase in caries over 3 yrs, taking into account changes occurring on individual tooth surfaces. Data for 3467 subjects were available for analyses at both baseline and year 3 examinations. Radiographs were taken for 1942 subjects at both baseline and year 3 examinations. The mean three-year clinical-only DMFS increment for the subjects using 1500-ppm-NaF pastes was 3.93, which was 6% lower than the corresponding mean of 4.19 for the 1000-ppm-NaF pastes. There was no significant difference between the mean DMFS increment for those using paste with or without TMP. Subjects who claimed to brush more frequently or who claimed not to use a tumbler to rinse after toothbrushing had lower three-year DFMS increments.

Riordan PJ, Fluoride supplements for young children: an analysis of the literature focusing on benefits and risks, Community Dentistry & Oral Epidemiology 27(1):72-83, 1999

The use of fluoride supplements to prevent caries has been advised for more than 100 years, but serious promotion of this strategy occurred only after the effectiveness of water fluoridation was established, in the late 1950s and 1960s. Although the effectiveness of fluoride supplements was apparently endorsed by many small clinical studies, closer examination of the experimental conditions of these, their methods and the analysis of their results undermined confidence in their findings. It is likely that confounding resulted in spurious conclusions in many of them. More modern, well-conducted clinical trials of supplements suggest that today, in children also exposed to fluoride from other sources such as toothpaste, the marginal effect of fluoride supplements is very small. There is evidence that fluoride lozenges, designed to maximise any local effect, may have a small caries preventive effect, particularly in deciduous teeth. Overall, poor compliance makes fluoride supplements a poor public health measure. Supplement use by young children is associated with a substantial risk of dental fluorosis. Fluorosis is an issue about which the public is becoming concerned in several countries and this concern, if translated into opposition to all fluoride use, could jeopardise the most successful caries preventive aid we have. The potential for dental fluorosis, concern about the public's reaction to this, the poor effectiveness of supplements and the public's poor compliance with their use are persuasive arguments for a radical reduction in the use of supplements by young children. Recent changes in fluoride dosage schedules and deferment of the age of commencing the use of supplements, implemented in many countries, have followed from these concerns. Supplements formulated as lozenges maximise topical exposure of enamel to fluoride and such products may offer older children and some adults a way of maintaining an elevated fluoride level in saliva at times when toothbrushing is not practical. [References: 71]

This paper assesses the risk from sugar consumption in a population of school children with low caries experience. It relates eight different measures of sugar consumption to the occurrence of any DMFS increment, and, separately, to approximal and pit-and-fissure DMFS. The data are from a 3-yr longitudinal study of 429 children, initially aged 11-15, residing in non-fluoridated rural communities in Michigan, USA. All children completed at least three dietary interviews, were present for baseline and final dental examinations, and had a parent or guardian provide questionnaire information on residence history, use of fluoride and dental services, and family history. Results indicated that a higher proportion of total energy intake from sugars increased the probability of caries on all surfaces, and a higher total intake of sugars was also associated with total caries increment. No relationship, however, was found between DMFS increment and the frequency of eating high sugar foods. Each additional 5 g of daily sugars intake was associated with a 1% increase in the probability of developing caries, and those whose energy intake from sugars was 1 SD above the mean had 2.0 times the risk of developing approximal caries than did children whose energy intake from sugars was 1 SD below the mean.

There is an extensive peer-reviewed literature on xylitol chewing gum as it pertains to effects on tooth decay in human subjects, on human dental plaque reduction, on inhibition of dental plaque acid production, on inhibition of the growth and metabolism of the mutans group of streptococci which are the prime causative agents of tooth decay, on reduction of tooth decay in experimental animals, and on xylitol's reported contribution to the remineralisation of teeth. The literature not only supports the conclusion that xylitol is non-cariogenic but it is now strongly suggestive that xylitol is caries inhibitory, that is, anti-cariogenic in human subjects, and it supplies reasonable mechanistic explanation(s).

[editor's note: could the increasing use of chewing gum be partially responsible for the dropping decay rates?]

A meta-analysis was performed on published data on the caries-inhibiting effect of fluoride gel treatment in 6- to 15-year-old children. The purposes of this meta-analysis were: (1) to calculate the overall caries-inhibiting effect of clinical fluoride gel treatment studies, based on explicit selection criteria, and (2) to explore factors potentially modifying the effect of fluoride gel treatment in caries prevention, concerning the baseline caries prevalence of the target population, the general fluoride regimen, and application features. The caries-inhibiting effect of fluoride gel application was assessed by the prevented fraction and the 'number needed to treat'. The overall prevented fraction of the fluoride gel treatment studies, indicating the reduction of caries incidence by fluoride gel treatment relative to the incidence in the control group, was 22% (95% CI = 18-25%). Multiple regression analysis showed no significant influence on the prevented fractions for the variables 'baseline caries prevalence', 'general fluoride regimen', 'application method', and 'application frequency'. The 'number needed to treat' (NNT), indicating the number of patients that need to be treated in order to prevent 1 DMFS, estimated the efficiency of fluoride gel treatment according to the caries incidence of the target population, including cost/effect relations. It was found that the NNT = 18 in a population with caries incidence 0.25 DMFS per year, and NNT = 3 in a population with caries incidence = 1.5 DMFS per year (treatment duration 1 year). From the standpoint of cost-effectiveness, the additional effect of fluoride gel treatment in current low and even moderate caries incidence child populations must be questioned.

The independent contributions of formula and water to the total fluoride (F) intake from the diet of formula-fed infants is not fully documented. Although the precise timing and mechanism by which dental fluorosis occurs has not been fully defined, water F levels can be an important consideration in the risk of dental fluorosis for formula-fed infants. An assessment of 1,308 participants younger than 2 years old revealed that: 81% of homes received public water; 19% received well water; 26% of participants used bottled water; and 11% used some kind of filtration system. In this study, virtually all formulas consumed by the birth cohort and water sources used in the reconstitution of these formulas were assayed for F using a F ion specific electrode and direct read method, except for soy-based formulas, which were analyzed by microdiffusion (modified Taves). Among 78 commercially available bottled waters in Iowa, F levels ranged from 0.02 to 1.36 ppm (mean 0.18 ppm), 83% from 0.02 to 0.16 ppm, 7% from 0.34 to 0.56 ppm, 1% had a F level of 0.88, and 9% had F levels > 1.0 ppm. Among 47 casein (milk)-based formulas, 16 ready-to-feed (RTF) formulas had levels of 0.04-0.55 ppm F (mean 0.17 ppm), 14 liquid concentrates (LC) reconstituted with distilled water had levels of 0.04-0.19 ppm F (mean 0.12 ppm), and 17 powdered concentrates (PC) reconstituted with distilled water had levels of 0.05-0.28 ppm F (mean 0.14 ppm). The 17 soy-based formulas had a range of 0.04-0.47 ppm F (mean 0.26 ppm).

A house to house survey in six rural villages in South India was conducted to asses the influence of undernutrition and environmental fluoride on deciduous dental eruption. Three villages surveyed were from the endemic fluorosis area where the estimated fluoride concentration was 5 +- 1.2 ppm. Oral cavities of all the children in the age group 5-48 months were examined and a tooth was marked erupted when it was visible emerging through the gingiva. Undernutrition, as classified by Gomez classification, was widely prevalent among preschool children in the surveyed area (n = 708; normal: 5.1%; grade-I 29.1%; grade-II. 53.1% and grade-III. 12.7%). Children in the severe grade of malnutrition possessed fewer teeth at a given age. Analysis of variance revealed that fluoride has significant (P < 0.005) detrimental effects on dental eruption among children in the 18-30 month age group. The efficacy of Bailey's formula (age in months =number of teeth erupted + 6) in indicating the chronological age was evaluated in the 5-24 month aged children (n=347). Bailey's formula failed to assess the age correctly in 87% with underassessment in 58% and overassessment in 29%. Its efficacy did not differ between the endemic and nonendemic areas. We conclude that i) undernutrition is a prevalent problem in rural areas in South India, ii) age calculation by Bailey's formula did not indicate the chronological age in the majority of children and hence is not useful in undernourished populations, and iii) undernutrition compounded by high water fluoride may delay the eruption of teeth. [emphasis added]

editor's note: delayed tooth eruption with higher fluoride intake means less cavities are recorded because teeth have not been exposed to cariogenic challenge for as long. Is this the "benefit" fluoridation proponents saw in the early "trials"? See related studies:

This study determined the effect of brushing with 0.4% stannous fluoride (SnF2) or 0.22% sodium fluoride (NaF) on clinical and microbial parameters associated with gingivitis. The study included three groups of 281 subjects. Subjects in all three groups were instructed to brush twice daily with an ADA-accepted fluoride dentifrice, rinse their mouths with water, and subsequently brush with 0.4% SnF2, 0.22% NaF, or a fluoridefree placebo gel. More stain was detected in the SnF2 group than in the other two groups at all periods except at baseline. However, no differences were observed in gingivitis, bleeding, or mean proportions of microbial forms in the SnF2 or NaF groups when compared with the placebo group at 18 months. Results indicate that 0.4% SnF2, or 0.22% NaF is no more effective than a placebo in reducing gingivitis.